[Spunky]

§ 1409. Children born out of wedlock
(a) The provisions of paragraphs (c), (d), (e), and (g) of section 1401 of this title, and of paragraph (2) of section 1408 of this title, shall apply as of the date of birth to a person born out of wedlock if—

This is addressing a person born out of wedlock, but they still had to fit in the critia as put forth on the date of their birth. In 1961 the citizen parent had to live in the U.S. 10 years. Five of those before the age of 16 and 5 after the age of 16. Since Barack was born when his mother was 18, she had not met the critera of the 5 years after the age of 16.

[Gondring]

And perhaps that’s the operative clause in this case. He said he didn’t look into that detail.

Also, note that things are different whether the father or mother is the citizen. The law didn’t always consider that.